It was the Duchess of Marlborough, of Blenheim Palace, the grandmother of Winston Churchill. Churchill's father, Randoph was the "spare". She had married into the British aristocracy for prestige: her husband had married her for money. There was little love lost between them, and so she did her "wifely duty" up to the point where teh Duke had an Heir and a spare (just in case anything tragic occured), and thereafter refused to play ball. One can see the resonances with teh case of Diana.